I was recently asked how I came across a particular book. "Oh, the algorithm recommended it to me," I answered. "The algorithm"? That sounds like the name of a mysterious agent, and that is how much contemporary talk treats it. But what is an algorithm? The 9th-century Persian mathematician al-Khwarizmi — from whose Latinized name the word algorithm derives — may help us with this question, for he was one of — if not the — first to formalize the idea of a set of instructions to solve a type of problem. So perhaps looking at his account of these instructions, his "algorithms," we might come to better understand our own unthinking responses like the one reported above. No sophisticated mathematical ability is required to learn deeply with and from the essay.